Sputtering target material

ABSTRACT

This invention provides sputtering target materials having high reflectance and excellent heat resistance, which are formed of Ag base alloys formed by adding a specific, minor amount of P to Ag and alloying them.

TECHNICAL FIELD

This invention relates to thin film-forming sputtering target materialhaving improved heat resistance while retaining high reflectance, and tothe thin film which is formed with use of the sputtering targetmaterial.

BACKGROUND ART

For reflection film or coating used on optical recording media such asCD (Compact Disc), DVD (Digital Versatile Disc), and the like orphoto-reflective conductive coating used on reflection type STN (SuperTwist Nematic) liquid crystal display devices, organic EL(Electroluminescence) display devices and the like, generally aluminum(Al) or Al alloys are used.

Such photoreflective thin film put to usages with those opticalrecording media, liquid crystal display devices, organic EL displaydevices and the like is generally prepared by making sputtering targetmaterial having desired properties, and film-forming using thesputtering target material by such methods as RF (radiofrequency)sputtering or DC (direct current) sputtering.

Thin films formed of Al or Al alloys which are prepared by such methodsexhibit moderate degrees of reflectance, low electrical resistance andfurthermore, stable corrosion resistance even in the air because passivestate films are formed in the surface layers. However, reflectance ofthin film made of Al or an Al alloy is, for example, around 80% of lighthaving a wavelength of 700 nm, which is not fully satisfactory for theusages requiring high reflectance.

It has been hence proposed to form thin films using gold (Au) or silver(Ag) as sputtering target material instead of Al or Al alloys, for e.g.,optical disc media represented by CD or DVD which require highreflectance. Also for reflection type STN liquid crystal displaydevices, use of Ag having high reflectance as the material for the thinfilm has been proposed.

Optical disc media represented by CD or DVD, reflection type STN liquidcrystal display devices and the like are liable to be exposed to hightemperatures under the conditions of their use. Where Ag is used, therearises a problem that the film may cause aggregation under hightemperatures, e.g., 200° C. or higher, to decrease the reflectance.

DISCLOSURE OF THE INVENTION

A main object of the present invention is to provide thin film-formingsputtering target material formed of Ag-base alloy, which exhibitsimproved heat resistance, while retaining high reflectance.

We have engaged in extensive research work with the view to achieve theabove object, to come to discover that an Ag base alloy exhibitingdrastically improved heat resistance while retaining the highreflectance characteristic of Ag can be obtained when a specific minoramount of phosphorus (P) is added and alloyed together; that an Ag basealloy exhibiting improved corrosion resistance as well as heatresistance can be obtained when each a minor amount of metallicelement(s) such as In, Sn, Zn, Au, Pt, Pd and the like is (are) added toAg, in addition to the specific minor amount of P, and alloyed together;and that heat resistance of the Ag base alloy can be further improvedwhen each a minor amount of such metallic element(s) as Cu, Ni, Fe, Biand the like is (are) added to Ag, in addition to the specific minoramount of P, and alloyed together. The present invention is whereuponcompleted.

Thus the present invention provides a thin film-forming sputteringtarget material having high reflectance, characterized by being made ofan Ag base alloy containing 0.005-1.0 mass % of P.

The invention also provides a thin film-forming sputtering targetmaterial having high reflectance, characterized by being made of an Agbase alloy containing 0.005-1.0 mass % of P and 0.01-2.0 mass % of atleast one metallic element selected from In, Sn and Zn.

The invention furthermore provides a thin film-forming sputtering targetmaterial having high reflectance, characterized by being made of an Agbase alloy containing 0.005-1.0 mass % of P, 0.01-0.9 mass % of Auand/or 0.01-5.0 mass % of Pd and/or 0.01-0.9 mass % of Pt.

The invention furthermore provides a thin film-forming sputtering targetmaterial having high reflectance, characterized by being made of an Agbase alloy containing 0.005-1.0 mass % of P and 0.01-5.0 mass % of atleast one metallic element selected from Cu, Ni, Fe and Bi.

The invention also provides a thin film-forming sputtering targetmaterial having high reflectance, characterized by being made of an Agbase alloy containing 0.005-1.0 mass % of P, 0.01-2.0 mass % of at leastone metallic element selected from In, Sn and Zn, 0.01-0.9 mass % of Auand/or 0.01-5.0 mass % of Pd and/or 0.01-0.9 mass % of Pt.

The invention also provides a thin film-forming sputtering targetmaterial having high reflectance, characterized by being made of an Agbase alloy containing 0.005-1.0 mass % of P, 0.01-2.0 mass % of at leastone metallic element selected from In, Sn and Zn, and 0.01-5.0 mass % ofat least one metallic element selected from Cu, Ni, Fe and Bi.

The invention also provides a thin film-forming sputtering targetmaterial having high reflectance, characterized by being made of an Agbase alloy containing 0.005-1.0 mass % of P, 0.01-0.9 mass % of Auand/or 0.01-5.0 mass % of Pd and/or 0.01-0.9 mass % of Pt, and 0.01-5.0mass % of at least one metallic element selected from Cu, Ni, Fe and Bi.

The invention also provides a thin film-forming sputtering targetmaterial having high reflectance, characterized by being made of an Agbase alloy containing 0.005-1.0 mass % of P, 0.01-2.0 mass % of at leastone metallic element selected from In, Sn and Zn, 0.01-0.9 mass % of Auand/or 0.01-5.0 mass % of Pd and/or 0.01-0.9 mass % of Pt, and 0.01-5.0mass % of at least one metallic element selected from Cu, Ni, Fe and Bi.

Hereinafter the thin film-forming sputtering target materials accordingto the invention are explained in further details.

The sputtering target materials of the invention are fundamentallycomposed of an Ag base alloy made by adding P to Ag as the base andalloying them. The use rate of P ranges 0.005-1.0 mass %, preferably0.01-0.75 mass %, in particular, 0.05-0.5 mass %.

A sputtering target material of the invention may be composed of ternaryAg base alloy formed by adding, to above Ag—P binary alloy components,at least one metallic element selected from In, Sn and Zn (hereafterreferred to as “(a) group metallic elements”) and alloying them. Theaddition ratio of the (a) group metallic element(s) can be each within arange of 0.01-2.0 mass %, preferably 0.05-1.75 mass %, in particular,0.1-1.5 mass %.

A sputtering target material of the invention may be composed of aternary Ag base alloy formed by adding, to above Ag—P binary alloycomponents, at least one metallic element selected from Au, Pd and Pt(hereafter referred to as “(b) group metallic elements”) and alloyingthem. The amount of the (b) group metallic element to be added is; forAu, within a range of 0.01-0.9 mass %, preferably 0.05-0.85 mass %, inparticular, 0.1-0.8 mass %; for Pd, 0.01-5.0 mass %, preferably 0.05-3.5mass % , in particular, 0.1-2.0 mass %; and for Pt, 0.01-0.9 mass %,preferably 0.05-0.85 mass %, in particular, 0.1-0.8 mass %.

A sputtering target material of the invention may also be composed of aternary Ag base alloy formed by adding, to the above Ag—P binary alloycomponents, at least one metallic element selected from Cu, Ni, Fe andBi (hereafter referred to as “(c) group metallic elements”) and alloyingthem. The amount of the (c) group metallic element(s) to be added can beeach within a range of 0.01-5.0 mass %, preferably 0.05-3.5 mass %, inparticular, 0.1-2.0 mass %.

A sputtering target material of the invention may also be composed of aquaternary Ag base alloy formed by adding, to the Ag—P binary alloycomponents, (a) group metallic element(s) and (b) group metallicelement(s) and alloying them. In such a quaternary Ag base alloy,addition ratio of the (a) group metallic element(s) may be each within arange of 0.01-2.0 mass %, preferably 0.05-1.75 mass %, in particular,0.1-1.5 mass %; and that of the (b) group metallic element(s) may bewithin a range of: for Au, 0.01-0.9 mass %, preferably 0.05-0.85 mass %,in particular, 0.1-0.8 mass %; for Pd, 0.01-5.0 mass %, preferably0.05-3.5 mass %, in particular, 0.1-2.0 mass %; and for Pt, 0.01-0.9mass %, preferably 0.05-0.85 mass %, in particular, 0.1-0.8 mass %.

A sputtering target material of the invention may also be composed of aquaternary Ag base alloy formed by adding, to the Ag—P binary alloycomponents, (a) group metallic element(s) and (c) group metallicelement(s) and alloying them. In this quaternary Ag base alloy, additionratio of (a) group metallic element(s) may be each within a range of0.01-2.0 mass %, preferably 0.05-1.75 mass %, in particular, 0.1-1.5mass %; and that of (c) group metallic element(s) may be each within arange of 0.01-5.0 mass %, preferably 0.05-3.5 mass %, in particular,0.1-2.0 mass %.

A sputtering target material of the invention may also be composed of aquaternary Ag base alloy formed by adding, to the Ag—P binary alloycomponents, (b) group metallic element(s) and (c) group metallicelement(s) and alloying them. In this quaternary Ag base alloy, additionratio of (b) group metallic element(s) may be within a range of: for Au,0.01-0.9 mass %, preferably 0.05-0.85 mass %, in particular, 0.1-0.8mass %; for Pd, 0.01-5.0 mass %, preferably 0.05-3.5 mass %, inparticular, 0.1-2.0 mass %; and for Pt, 0.01-0.9 mass %, preferably0.05-0.85 mass %, in particular, 0.1-0.8 mass %; and that of (c) groupmetallic element(s) may be each within a range of 0.01-5.0 mass %,preferably 0.05-3.5 mass %, in particular, 0.1-2.0 mass %.

A sputtering target material of the invention may also be composed of aquinary Ag base alloy formed by adding, to above Ag—P binary alloycomponents, three components of (a) group metallic element(s), (b) groupmetallic element(s) and (c) group metallic element(s) and alloying them.In this quinary Ag base alloy the addition ratio of (a) group metallicelement(s) to be added can be each within a range of 0.01-2.0 mass %,preferably 0.05-1.75 mass %, in particular, 0.1-1.5 mass %; that of the(b) group metallic element(s) may be within a range of, for Au, 0.01-0.9mass %, preferably 0.05-0.85 mass %, in particular, 0.1-0.8 mass %; forPd, 0.01-5.0 mass %, preferably 0.05-3.5 mass % , in particular, 0.1-2.0mass %; and for Pt, 0.01-0.9 mass %, preferably 0.05-0.85 mass %, inparticular, 0.1-0.8 mass %; and that of (c) group metallic element(s)may be each within a range of 0.01-5.0 mass %, preferably 0.05-3.5 mass%, in particular, 0.1-2.0 mass %.

Those Ag base alloys according to the invention can be prepared by thoseper se known methods, for example, by adding P to Ag; or adding (a)group metallic element(s) to Ag and P; or (b) group metallic element(s)to Ag and P; or (c) group metallic element(s) to Ag and P; or (a) groupmetallic element(s) and (b) group metallic element(s) to Ag and P; or(a) group metallic element(s) and (c) group metallic element(s) to Agand P; or (b) group metallic element(s) and (c) group metallicelement(s) to Ag and P; or (a) group, (b) group and (c) group metallicelements to Ag and P, each in the amount as specified in the above; andmelting them together in a suitable metal melting furnace such as gasoven, high frequency melting furnace or the like, at temperatures ofabout 1,000-about 1,200° C. The melting atmosphere may be that of air,or of an inert gas or in vaquo where necessary.

Ag, which is the main starting material, may be that which is marketedin such forms as granule, plate, block or the like, normally havingpurity of at least 99.95%, preferably at least 99.99%. Also as thoseadditive elements of P, In, Sn, Zn, Au, Pd, Pt, Cu, Ni, Fe and Bi, thosemarketed in such forms as powder, granule, plate, block and the like canbe used. Normally those having purity of at least 99.9%, preferably thatof at least 99.95%, are conveniently used.

Thus, binary to quinary Ag base alloys containing in Ag, P, or P and (a)group metallic element(s), or P and (b) group metallic element(s), or Pand (c) group metallic element(s), or P, (a) group metallic element(s)and (b) group metallic element(s), or P, (a) group metallic element(s)and (c) group metallic element(s), or P, (b) group metallic element(s)and (c) group metallic element(s), or P, (a) group metallic element(s),(b) group metallic element(s) and (c) group metallic element(s), each atthe respectively specified ratios. Sputtering target materials composedof those Ag base alloys maintain the high reflectance inherent in Ag andstill in addition have drastically improved heat resistance over that ofconventional Ag.

The sputtering target materials composed of the Ag base alloys accordingto the present invention, therefore, can be advantageously used forreflection coatings of optical disc media represented by CD and DVD forwhich high reflectance is required, and also for photo-reflective thinfilms in reflection type STN liquid crystal display devices or organicEL display devices.

Also for their use in those optical disc media represented by CD or DVDand reflection type STN liquid crystal display or organic EL displaydevices, corrosion resistance is required under their using conditions.

Ag—P binary alloys exhibit approximately equivalent sulfurizationresistance or corrosion resistance to halogen elements to those of Ag.Whereas, it has been confirmed through experiments that addition of the(a) group metallic element and/or (b) group metallic element improvesthe corrosion resistance to exceed that of Ag.

Formulation of reflection coating from those sputtering target materialscomposed of Ag base alloys of the present invention can be conducted byany of sputtering methods known per se, for example, radiofrequency (RF)sputtering method, direct current (DC) sputtering method, magnetronsputtering method and the like.

Hereinafter the present invention is explained more specifically,referring to working examples.

EXAMPLES 1-1 TO 1-14 AND COMPARATIVE EXAMPLES 1-1 TO 1-3

To Ag and P, optionally at least one of In, Sn, Zn, Au, Pd, Pt, Cu, Ni,Fe and Bi was added, melted together in a gas oven at a temperature ofabout 1200° C., and the resulting melts were cast-processed to preparesputtering target materials each having the composition as shown inTable 1. Also from those compositions of Comparative Examples,sputtering target materials were prepared in the similar manner.

TABLE 1 Sample No. Composition Example 1-1 Ag-0.008 mass % P 1-2 Ag-0.13mass % P 1-3 Ag-0.07 mass % P-0.40 mass % Cu 1-4 Ag-0.15 mass % P-0.85mass % Cu 1-5 Ag-0.30 mass % P-1.70 mass % Cu 1-6 Ag-0.12 mass % P-0.80mass % Zn 1-7 Ag-0.05 mass % P-0.80 mass % In 1-8 Ag-0.15 mass % P-0.85mass % Cu-0.15 mass % Au 1-9 Ag-0.15 mass % P-0.85 mass % Cu-0.15 mass %Pd 1-10 Ag-0.11 mass % P-0.05 mass % Ni 1-11 Ag-0.04 mass % P-0.2 mass %In-0.8 mass % Pd 1-12 Ag-0.15 mass % P-0.5 mass % In-0.2 mass % Pd-0.85mass % Cu 1-13 Ag-0.15 mass % P-0.85 mass % Cu-0.4 mass % Bi 1-14Ag-0.15 mass % P-0.85 mass % Cu-0.05 mass % Fe Comparative 1-1 AgExample 1-2 Ag-0.5 mass % Au 1-3 Ag-1.0 mass % Zn

For heat resistance examination, those sputtering target materials ofthe compositions as given in Table 1 were used to each form a thin filmon a glass substrate plate to a film thickness of 150 nm byradiofrequency (RF) sputtering method, and heat resistance of the formedfilm was examined.

The examination method was as follows: after measuring reflectance ofthe film, the film was heat-treated at 200° C. in the air for an hourand its reflectance was measured once again. The variation ratio in thereflectance before and after the heat treatment was calculated accordingto the following equation:

variation ratio (%)=100−(reflectance after the test/reflectance beforethe test×100).

The results were as shown in Table 2.

TABLE 2 Variation Ratio in Reflectance (%) Measuring Measuring Samplewavelength wavelength No. 400 nm 700 nm Example 1-1 1.4 0.0 1-2 0.0 0.01-3 0.0 0.0 1-4 0.0 0.0 1-5 0.0 0.0 1-6 0.0 0.0 1-7 1.2 0.0 1-8 0.0 0.01-9 0.0 0.0  1-10 0.0 0.0  1-11 0.6 0.0  1-12 0.0 0.0  1-13 0.0 0.0 1-14 0.0 0.0 Comparative 1-1 5.2 0.5 Example 1-2 4.2 0.1 1-3 3.2 0.1

As seen in Table 2, where the measuring wavelength was 700 nm verylittle difference was observed in variation ratio in reflectance ofmeasured samples, but when the measuring wavelength was 400 nm,reflectance dropped in Comparative Examples 1-1 to 1-3. By contrast,there was nearly no decrease in reflectance in Examples 1-1 to 1-14, andit can be understood that the products of the invention excel in heatresistance.

For further investigating heat resistance, those thin films prepared inidentical manner with the above were heat treated in the air at 250° C.for an hour and the variation ratio in their reflectance was determinedin the identical manner. The results were as shown in Table 3.

TABLE 3 Variation Ratio in Reflectance (%) Measuring Measuring Samplewavelength wavelength No. 400 nm 700 nm Example 1-1 3.8 0.0 1-2 1.2 0.01-3 0.1 0.0 1-4 0.0 0.0 1-5 0.0 0.0 1-6 0.6 0.0 1-7 3.2 0.0 1-8 0.0 0.01-9 0.0 0.0  1-10 0.1 0.0  1-11 1.5 0.0  1-12 0.0 0.0  1-13 0.0 0.0 1-14 0.0 0.0 Comparative 1-1 16.0  1.0 Example 1-2 6.9 0.1 1-3 5.3 0.0

As seen in Table 3, where the measuring wavelength was 700 nm, verylittle difference was observed in variation ratio in reflectance ofmeasured samples, but when the measuring wavelength was 400 nm, decreasein reflectance of those thin films of Examples 1-1 to 1-14 wassuppressed compared with that in the thin films of Comparative Examples1-1 to 1-3. Thus it can be understood that the films of the inventionare by far superior in heat resistance.

EXAMPLES 2-1 TO 2-5 AND COMPARATIVE EXAMPLES 2-1 TO 2-2

Under actual use conditions, improvement in corrosion resistance, inparticular, sulfurization resistance, is occasionally required. Hence,sputtering target materials of the compositions as shown in thefollowing Table 4 were prepared in the identical manner with theforegoing Examples, and their sulfurization resistance was examined.

The examination method was as follows. Using those sputtering targetmaterials, films were formed on glass substrate plates to a thickness of150 nm by radio frequency (RF) sputtering method. After measuringreflectance of the films, the films were immersed in 0.01% aqueoussolution of sodium sulfide (Na₂S) for an hour and thereafter theirreflectance was measured once again. The variation ratio in reflectanceof the thin films before and after the immersion was calculatedaccording to the following equation:

variation ratio (%)=100−(reflectance after the test/reflectance beforethe test×100).

The results were as shown in Table 5.

TABLE 4 Sample No. Composition Example 2-1 Ag-0.12 mass % P-0.80 mass %Zn 2-2 Ag-0.05 mass % P-0.80 mass % In 2-3 Ag-0.05 mass % P-0.80 mass %In 2-4 Ag-0.04 mass % P-0.2 mass % In-0.8 mass % Pd 2-5 Ag-0.15 mass %P-0.5 mass % In-0.2 mass % Pd-0.85 mass % Cu Comparative 2-1 Ag Example2-2 Ag-0.5 mass % Au

TABLE 5 Variation Ratio in Reflectance (%) After the test MeasuringMeasuring Sample wavelength wavelength No. 400 nm 700 nm Example 2-1 4618 2-2 44 18 2-3 45 18 2-4 45 16 2-5 41 17 Comparative 2-1 61 38 Example2-2 61 35

It can be understood from Table 5 that decrease in reflectance wassuppressed in the thin films of Examples 2-1 to 2-5 in which In, Sn, Zn,etc. were added, compared with that in the films of Comparative Examples2-1 to 2-2, and the products according to the invention excel insulfurization resistance.

EXAMPLES 3-1 TO 3-2 AND COMPARATIVE EXAMPLE 3-1

Under actual using environments, improvement in chlorine resistance mayalso be required, and examination of chlorine resistance was conducted.

The examination method was as follows. Sputtering target materials ofthe compositions as specified in Table 6 were prepared, which were thenused to form films on glass substrate plates to a thickness of 150 nm byradiofrequency (RF) sputtering method. The films were measured of theirreflectance, immersed in 3% aqueous solution of sodium chloride (NaCl)for 10 minutes, and measured of reflectance once again. The variationratio in the reflectance of the thin films before and after theimmersion was calculated according to the following equation:

variation ratio (%)=100−(reflectance after the test/reflectance beforethe test×100).

The results were as shown in Table 7.

TABLE 6 Sample No. Composition Example 3-1 Ag-0.15 mass % P-0.85 mass %Cu-0.15 mass % Au 3-2 Ag-0.15 mass % P-0.85 mass % Cu-0.15 mass % PdComparative 3-1 Ag Example

TABLE 7 Variation Ratio in Reflectance (%) After the test MeasuringMeasuring Sample wavelength wavelength No. 400 nm 700 nm Example 3-1 0.40.0 3-2 0.3 0.0 Comparative 3-1 3.4 0.0 Example

It can be understood from Table 7 that decrease in reflectance wassuppressed in the thin films of Examples 3-1 to 3-2 in which Au, Pd,etc. were added, compared with that in the film of Comparative Example3-1, and that the products according to the invention excel in chlorineresistance.

1-2. (canceled)
 3. A sputtering target material for forming a thin filmhaving high reflectance, said material being an Ag base alloy consistingof Ag having a purity of at least 99.95%, 0.008-1.0 mass % of P,0.01-0.9 mass % of Au, and 0.01-5.0 mass % of at least one metallicelement selected from Cu and Bi, and P, Au, Cu and Bi having a purity ofat least 99.9%. 4-5. (canceled)
 6. Thin film formed from the material ofclaim 3.